The present invention relates to a contact type color image sensor suitable for an image scanner for reading image information.
As a conventional contact type color image sensor, a structure shown in a sectional view of FIG. 7 is known. Differently colored color filters 3 are formed on the surface of light receiving elements of a linear image sensor 6. A document 10 is irradiated with a lighting device such as a white fluorescent lamp 8, and the reflected light is received through the different color filters 3 by the light receiving elements to perform color separation.
However, since the surface of an IC of the linear image sensor is uneven, it is difficult to form on the light receiving elements of the IC the different color filters with the same film thickness and transmittance. Flattening techniques for moderating the surface unevenness have a strong effect in raising the cost of the product.
In order to solve the above problem, according to the present invention, color filters are formed on a surface on a document side of a transparent protective glass in direct contact with a document for flattening the light irradiation surface, such that the pitch thereof equals to that of light receiving elements of a linear image sensor. Further, in order to improve the color separation capability, the area of an opening of a unit light receiving element is made to be smaller than the area of a unit pixel of the color filters. Further, in order that light is irradiated onto a surface of a document through a part of the filters or through the space between the document and the filters, white scattering thin films are arranged and formed in proximity to the filters so as to sandwich the filters in a main scanning direction. Further, in order to eliminate abrasion of the color filters and of the white scattering thin films, the surface of the filters and the surface of the white scattering thin films are covered with a thin transparent insulating film. Further, by using a solid light source instead of a white fluorescent lamp, the shock resistance against dropping and the like is improved.